Railroad flat cars are used to transport highway trailers from one place to another in what is referred to as intermodal Trailer-on-Flat-Car (TOFC) service. TOFC service competes with intermodal container service known as Container-on-Flat-Car (COFC), and with truck trailers driven on the highway. TOFC service has been in relative decline for some years due to a number of disadvantages.
First, for distances of less than about 500 miles (800 km), TOFC service is thought to be slower and less flexible than highway operation. Second, in terms of lading per rail car, TOFC tends to be less efficient than Container-on-Flat-Car (COFC) service, and tends also to be less efficient than double-stack COFC service in which containers are carried on top of each other. Third, TOFC (and COFC) terminals tend to require significant capital outlays. Fourth, TOFC loading tends to take a relatively long time to permit rail road cars to be shunted to the right tracks, for trailers to be unloaded from incoming cars, for other trailers to be loaded, and for the rail road cars to be shunted again to make up a new train consist. Fifth, shock and other dynamic loads imparted during shunting and train operation may tend to damage the lading. It would be advantageous to improve rail road car equipment to reduce or eliminate some of these disadvantages.
As highways have become more crowded, demand for a fast TOFC service has increased. Recently, there has been an effort to reduce the loading and unloading time in TOFC service, and an effort to increase the length of TOFC trains. There are two methods for loading highway trailers on flat cars. First, they can be side-loaded with an overhead crane or side-lifting fork-lift crane. Loading with overhead cranes, or with specialized fork-lift equipment tends to occur at large yards, and tends to be capital intensive.
The second method of loading highway trailers, or other wheeled vehicles, onto rail road cars having decks for carrying vehicles, is by end-loading. End-loading, or circus loading as it is called, has two main variations. First, a string of cars can be backed up to a permanently fixed loading dock, typically a concrete structure having a deck level with the deck of the rail cars. Alternatively, a movable ramp can be placed at one end of a string of rail car units. In either case, the vehicles are driven onto the rail road cars from one end. Each vehicle can be loaded in sequence by driving (in the case of highway trailers, by driving the trailers backward) along the decks of the rail road car units. The gaps between successive rail car units are spanned by bridge plates that permit vehicles to be driven from one rail car unit to the next. Although circus loading is common for a string of cars, end-loading can be used for individual rail car units, or multiple rail car units as may be convenient.
One way to reduce shunting time, and to run a more cost effective service is to operate a dedicated unit train of TOFC cars whose cars are only rarely uncoupled. However, as the number of units in the train increases, circus loading becomes less attractive, since a greater proportion of loading time is spent running a towing rig back and forth along an empty string of cars. It is therefore advantageous to break the unit train in several places when loading and unloading. Although multiple fixed platforms have been used, each fixed platform requires a corresponding dedicated dead-end siding to which a separate portion of train can be shunted. It is not advantageous to require a large number of dedicated parallel sidings with a relatively large fixed investment in concrete platforms.
To avoid shunting to different tracks, as required if a plurality of fixed platforms is used, it is advantageous to break a unit train of TOFC rail road cars on a single siding, so that the train can be re-assembled without switching from one track to another. For example, using a 5000 or 6000 ft siding, a train having 60 rail car units in sections of 15 units made up of three coupled five-pack articulated cars, can be split at two places, namely fifteen units from each end, permitting the sequential loading of fifteen units per section to either side of each split. Once loaded, the gaps between the splits can be closed, without shunting cars from one siding to another. Use of a single siding is made possible by moving the ramps to the split location, rather than switching strings of cars to fixed platforms.
In using movable ramps for loading, the highway trailers are typically backed onto the railcars using a special rail yard truck, called a hostler truck. Railcars can be equipped with a collapsible highway trailer kingpin stand. When the highway trailer is in the right position, the hostler truck hooks onto the collapsible stand (or hitch) and pulls it forward, thereby lifting it to a deployed (i.e., raised) and locked position. The hostler truck is then used to push the trailer back to engage the kingpin of the hitch. The landing gear of the highway trailer is lowered, and, in addition, it is cranked downward firmly against the rail road car deck as a safety measure in the event of a hitch failure or the king pin of the trailer is sheared off. Once one trailer has been loaded, the towing rig, namely the hostler truck, drives back to the end of the string, another trailer is backed into place, and the process is repeated until all of the trailers have been loaded in the successive positions on the string of railcars. Unloading involves the same process, in reverse. In some circumstances circus loaded flat cars can be loaded with trucks, tractors, farm machinery, construction equipment or automobiles, in a similar manner, except that it is not always necessary to use a towing rig.
From time to time the train consist may be broken up, with various highway-trailer-carrying rail road cars being disconnected, and others being joined. Bridge plates have been the source of some difficulties at the rail car ends where adjacent railroad cars are connected, given the nomenclature “the coupler ends”. Traditionally, a pair of cars to be joined at a coupler would each be equipped with one bridge plate permanently mounted on a hinged connection on one side of the car, typically the left hand side. In this arrangement the axis of the hinge is horizontal and transverse to the longitudinal centerline of the rail car.
Conventionally, for loading and unloading operations, the bridge plate of each car at the respective coupled end is lowered, like a draw bridge, into a generally horizontal arrangement to mate with the adjoining car, each plate providing one side of the path so that the co-operative effect of the two plates is to provide a pair of tracks along which a vehicle can roll. When loading is complete, the bridge plates are pivoted about their hinges to a generally vertical, or raised, position, and locked in place so that they cannot fall back down accidentally.
Conventionally, bridge plates at the coupler ends are returned to the raised, or vertical, position before the train can move, to avoid the tendency to become jammed or damaged during travel. That is, as the train travels through a curve, the bridge plates would tend to break off if left in the spanning position between the coupler ends of two rail road cars. Since bridge plates carry multi-ton loads, they tend to have significant structure and weight. Consequently, the requirement to raise and lower the bridge plates into position is a time consuming manual task contributing to the relatively long time required for loading and unloading. Raising and lowering bridge plates may tend to expose rail-yard personnel to both accidents and repetitive strain injuries caused by lifting.
It would be advantageous to have (a) a bridge plate that can be moved to a storage, or stowed, position, with less lifting; (b) a bridge plate system that does not require the bridge plate to be moved by hand as often, such as by permitting the bridge plate to remain in place during train operation, rather than having to be lowered every time the train is loaded and unloaded, and raised again before the train can move.
Further, a rail road car may sometimes be an internal car, with its bridge plates extended to neighbouring cars, and at other times the rail road car may be an “end” car at which the unit train is either (a) split for loading and unloading; (b) coupled to the locomotive; or (c) coupled to another type of rail road car. In each case, the bridge plate at the split does not need to be in an extended “drive-over” position, and should be in a stowed position. Therefore it is advantageous to have a rail car with bridge plates that can remain in position during operation as an internal car in a unit train, and that can also be stowed as necessary when the car is placed in an end or split position.
However, a bridge plate that is to be left in place to span a gap between adjacent releasably coupled vehicle carrying rail road cars while the train is moving must be able to accommodate relative pitch, yaw, roll and slack action motions between the coupler ends of two adjacent cars during travel. For example, when a train travels through a curve, the gap spanned by the bridge plate on the inside of the curve will shorten, and the gap spanned by the bridge plate on the outside of the curve will lengthen. When passing over switches, the coupler ends of adjacent railroad cars may be subject to both angular and transverse displacement relative to each other. All of these displacements are complicated by the need to tolerate slack action. Slack action includes not only the actual slack in the couplers themselves, but also the run-in and run-out of the draft gear, (or sliding sills, or end of car cushioning devices) of successive rail cars in the train. This combination of displacements does not occur at the articulated connectors between units of an articulated rail road car (which are joined at a common, virtually slackless pin), but does occur at the coupler ends. If the vehicle carrying rail road cars have long travel draft gear, such as sliding sills or long travel end of car cushioning (EOCC) units, the potential range of motion that would have to be tolerated by stay-in-place bridge plates at the “drive-over” coupler ends of railroad cars would be quite large relative to the nominal gap to be spanned with the cars at an undeflected equilibrium on straight, flat track.
One approach is to reduce the amount and type of train motion to which stay-in-place bridge plates may be subjected. It is advantageous to reduce the amount of slack in the releasable coupling, as by using a low slack, or slackless coupler, and to reduce the travel in the draft gear, as by using reduced travel draft gear. In addition, reduction in overall slack action in the train has a direct benefit in improving ride quality, and hence reducing damage to lading.
One way to reduce slack action is to use fewer couplings. To that end, since articulated connectors are slackless, and since the consist of a unit train changes only infrequently, the use of articulated rail road cars significantly reduces the slack action in the train. Some releasable couplings are still necessary, since the consist does sometimes change, and it is necessary to be able to change out a car for repair or maintenance when required.
Reduction in the travel of draft gear or end-of-car cushioning units (EOCC) runs directly counter to the development of draft gear since the 1920's or 1930's. There has been a long history of development of longer travel draft gear to provide lading protection for relatively high value lading requiring gentler handling, in particular automobiles and auto parts, but also farm machinery, or tractors, or highway trailers. There are, or were, a number of factors that led to this tendency. First, if subject to general classification in a switching yard, the vehicle carrying rail road cars could be coupled to other types of car, rather than merely other vehicle carrying cars. As such, they would be subject to slack run-in (i.e, buff) loads imposed by grain cars, gondola cars, box cars, centerbeam cars, and so on. That is, they were exposed to buff loads from cars having the full range of slack of Type-E couplers, and the full range of travel of conventional draft gear. Second, if subject to flat switching, the often less than gentle habits of rail yard personnel might lead to rather high impact loads during coupling.
In such a hostile operating environment, long travel draft gear or long travel EOCC units are the customary means for protecting the more fragile types of lading. Historically, common types of draft gear, such as that complying with, for example, AAR specification M-901-G, have been rated to withstand an impact at 5 m.p.h. (8 km/h) at a coupler force of 500,000 Lb. (roughly 2.2×106 N). Typically, these draft gear have a travel of 2¾ to 3¼ inches in buff before reaching the 500,000 Lb. load, and before “going solid”. The term “going solid” refers to the point at which the draft gear exhibits a steep increase in resistance to further displacement. While deflection of about 3 inches at 500,000 lbs. buff load may be acceptable for coal or grain, it implies undesirably high levels of deceleration or acceleration for more fragile lading, such as automobiles or auto parts. If the impact is sufficiently large to make the draft gear “go solid”, then the force transmitted, and the corresponding acceleration imposed on the lading, increases sharply.
Draft gear development has tended to be directed toward providing longer travel on impact to reduce the peak acceleration. In the development of sliding sills, and latterly, hydraulic end of car cushioning units, the same impact is accommodated over 10, 15, or 18 inches of travel. Given this historical development, it is counter-intuitive to employ short-travel, or ultra short travel, draft gear for carrying wheeled vehicles. However, aside from facilitating the use of stay-in-place coupler end bridge plates, the use of short travel, or ultra-short travel, buff gear has the advantage of eliminating the need for relatively expensive, and relatively complicated EOCC units, and the fittings required to accommodate them. This may tend to permit savings both at the time of manufacture, and savings in maintenance during service.
Short travel draft gear is presently available. As noted above, most M-901-G draft gear “go solid” at an official rating travel of 2¾″ to 3¼″ of compression under a buff load of 500,000 lbs. Mini-BuffGear, as produced by Miner Enterprises Inc., of 1200 State Street, Geneva Ill., appears to have a displacement of less than 0.7 inches at a buff load of over 700,000 lbs., and a dynamic load capacity of 1.25 million pounds at 1 inch travel.
In addition to M-901-G draft gear, and Mini-BuffGear, it is also possible to obtain draft gear having less than 1¾ inches of deflection at 450,000 Lbs., one type having about 1.6 inches of deflection at 450,000 Lbs. This is a significant difference from most M-901-G draft gear.
Furthermore, in seeking a low slack, or slackless train, it is desirable to adopt low-slack, or slackless couplings. Although reduced slack AAR Type F couplers have been known since the 1950's, and slackless “tightlock” AAR Type H couplers became an adopted standard type on passenger equipment in 1947, AAR Type E couplers are still predominant. AAR Type H couplers are expensive, and are used for passenger cars, as are the alternate standard Type CS controlled slack couplers. According to the 1997 Cyclopedia, supra, at p. 647 “Although it was anticipated at one time that the F type coupler might replace the E as the standard freight car coupler, the additional cost of the coupler and its components, and of the car structure required to accommodate it, have led to its being used primarily for special applications”. One “special application” for F type couplers is in tank cars.
The difference between the nominal ⅜″ slack of a Type F coupler and the nominal 25/32″ slack of a Type E coupler may seem small in the context of EOCC equipped cars having 10, 15 or 18 inches of travel. By contrast, that difference, 13/32″, seems proportionately larger when viewed in the context of the approximately 11/16″ buff compression (at 700,000 lbs.) of Mini-BuffGear. It should be noted that there are many different styles of Type E and Type F couplers, whether short or long shank, whether having upper or lower shelves. There is a Type E/F having a Type E coupler head and a Type F shank. There is a Type ESOARE knuckle which reduces slack from 25/32″ to 20/32″. Type F herein is intended to include all variants of the Type F series, and Type E herein is intended to include all variants of the Type E series having 20/32″ of slack or more.
Stay-in-place bridge plates are intended to accommodate the range of travel defined by the combination of coupler and draft gear, given anticipated service loads. While it may be possible to operate telescoping bridge plates, they are relatively less advantageous than monolithic bridge plates. First, a telescoping device may require a more challenging installation procedure if two sliding parts have to be inserted in each other. Second, the telescoping device must be able to telescope, and yet must also be able to support the vertical load carried on the slide. A slide with significant tolerance may not necessarily support bending moments well, may tend to wear under repeated loading, and may cease to slide very well if damaged or bent due to the vertical loads. A monolithic beam has no moving parts requiring careful manufacturing tolerance, and has no moving parts that may deform and jam in service. Slides may accumulate sand and dirt, and may cease to function if water is able to freeze in the slide.
Loading and unloading of highway trailers, or other vehicles in the manner described, above, can also be a relatively tedious and time consuming chore, particularly as the number of railroad cars in the string increases. Persons engaged in such activity may, after some time, perhaps late at night, tend to become less fastidious in their conduct. They may tend to become overconfident in their abilities, and may tend to try to back the highway trailers on to the rail cars rather more quickly than may be prudent. It has been suggested that speeds in the order of 20 km/h have been attempted. In the past, it has been difficult to form bridge plates that lie roughly flush with the deck. Due to their strength requirement, they tend to be about 2 inches thick or more. As a result there is often a significant bump at the bridge plate. Aggressive loading and unloading of the trailers may cause an undesirable impact at the bump, and loss of control of the load. In that regard, it would be advantageous to reduce the height or severity of the bump. It is also advantageous to employ side sills that have a portion, such as the side sill top chord, that extends above the height of the deck and acts as a curb bounding the trackway, or roadway, defined between the side sills. It is also helpful to have flared sill, or curb, ends that may tend to aid in urging highway trailers toward the center of the trackway along the rail cars.
Demand for transport by TOFC or by container may fluctuate over time. Therefore it would be advantageous to be able to convert a rail road car from one type of service to the other. To that end it would be advantageous to have a rail road car that has structure for either service, and that permits subsequent conversion as may be desired according to market conditions.
Reference is made herein to shipping containers and various sizes of highway trailers. Shipping containers come in International Standards Association (ISO) sizes, or domestic sizes. The ISO containers are 8′-0″ wide, 8′-6″ high, and come in a 20′-0″ length weighing up to 52,900 Lbs., or a 40′-0″ length weighing up to 67,200 Lbs., fully loaded. Domestic containers are 8′-6″ wide and 9′-6″ high. Their standard lengths are 45′, 48′, and 53′. All domestic containers have a maximum fully loaded weight of 67,200 Lbs. Some common sizes of highway trailers are, first the 28′ pup trailer weighing up to 40,000 Lbs., and the 45′ to 53′ trailer weighing up to 65,000 Lbs. for a two axle trailer and up to 90,000 Lbs. for a three axle trailer.